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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

LINSEED OIL

403

with sulphur dioxide or chlorine ; the reaction of the liquid fatty acids with
silver nitrate (Tortelli and Ruggeri) is given, although in an attenuated form,
by oils which have been heated to 250 for 10-20 minutes. This observation
is, however, of little practical value, since cottonseed oil treated in this way
is scarcely utilisable, at any rate for mixing with comestible olive oil.

It is also to be noted that kapok and baobab oils give the same reactions
as cottonseed oil, both with silver nitrate and with the carbon disulphide re-
agent, but even far more intensely (with silver nitrate the reaction occurs even
in the cold and with Halphen's reagent, i% of kapok oil mixed with other oil
gives almost the same coloration as pure cottonseed oil). Kapok oil may,
according to Milliau,1 be distinguished from cottonseed oil by means of the
action, of silver nitrate on the fatty acids in the cold ; but actually the fatty
acids of cottonseed oil also slowly reduce silver nitrate in the cold and, in the
case of mixtures, the reaction may be due as much to a little kapok oil as to
a large amount of cottonseed oil. For a more certain indication other data
must be employed. For instance, with mixtures of olive and arachis oils, the
iodine number and other constants will show if the proportion of the extraneous
oil is large or small. Thus, an arachis oil which gives Halphen's reaction as
sharply and intensely as pure cottonseed oil but has a normal iodine number
and a normal content of arachidic and lignoceric acids cannot possibly contain
an amount of cottonseed oil capable of giving such an intense colour reaction ;
it is, therefore, more probable that such an oil is contaminated with a little
kapok oil than with much cottonseed oil.

Comestible cottonseed oil should show little colour and no unpleasant smell
or taste and no acidity. The industrial oil should have: D = 0-922-0-930,
iodine number = 103-110, solidification point of the fatty acids = 32-40,
Maumene number (Tortelli) = 78-8.

Refinery residues of cottonseed oil (soapstock), which are pasty and brownish-
yellow to black, are valued on the basis of their total content of fatty matter
(standard 50%), for the determination of which, see General Part, i, A-C.

Cottonseed margarine or stearine is the solid part which separates on cooling
the oil and is recovered from the latter by pressure at 10-11 ; it is white or
yellowish, has the consistency of butter (m.p. 16-32) and gives the same colour
reactions as cottonseed oil. Its specific gravity at 100 is 0-864-0-868, saponi-
fication number 194-195, iodine number 95-96. Its value depends on the
titer (solidifying point of the fatty acids ; see Tallow) and on the content of
total fatty matter (see General Part, i, A-C).

LINSEED   OIL

Ordinary or crude linseed oil (for boiled linseed oil, see next chapter:
Industrial Products of the Treatment of Fatty Matters), from the seeds of
Linum usitatissimum., is yellow or brownish-yellow and has a peculiar odour
and an unpleasant taste. It dissolves in about 40 parts of cold or 5 parts
of boiling absolute alcohol. It contains a certain quantity of unsaponifiable
substances (1-1-3%). Its physical and chemical characters are given in
Table XLIV.

It is coloured deep orange with brown striae by Heydenreich's reagent
and soon sets to a black, tarry skin. By Hauchecorne's or Brulle"s reagent
it is coloured an intense brownish-red. Besides determinations of the

1 .Ann, de chim. analyt., 1905, p. 9,                                                                             25	3-66